2600K stuck at 1.6Ghz

Something is very wrong with the replacement Z68A-GD65 G3 they sent me yesterday. No matter what I do, Cpu-Z always reports 1.6Ghz for the CPU. The VCore shows up properly but the CPU never really gets out of the idle 1.6Ghz. Also temperatures don't disagree with that, the cpu never gets above 40°C even with 1.5V VCore, which normally leads to something 70°C'ish in Prime blend.

I've tried manual OC and the automatic OC feature of the board in various BIOS revisions including the old Beta that I've used on the original board that was defective but no luck.

Any ideas what I could check before wrapping things up and go request another RMA?

Turning C1E and EIST off sadly didn't help. When doing manual OC I had disabled it anyway but even with default settings it should reach 3.4Ghz or 3.5Ghz at full load when using the default Turbo feature, EIST and C1E on or off.
This is the current situation at full load: cpu-z validation

Turning C1E and EIST off sadly didn't help. When doing manual OC I had disabled it anyway but even with default settings it should reach 3.4Ghz or 3.5Ghz at full load when using the default Turbo feature, EIST and C1E on or off.
This is the current situation at full load: cpu-z validation

try turning off the C states as well. C3 and C6, they are both power saving features in the bios.